Been running this setup since 2010. 10 BTDC is about right for a carbureted engine due to the 1) rich mixture and 2) need to start the burn early due to poor mixing at low speeds. 33 BTDC would be conservative as well. And better than 28 BTDC.

Computer failures suck, and could happen, but that's no reason not to do it. That's just fear mongering of a low probability mode of failure. I'd be more worried about cellphone drivers.

I knew we would get the old school CDI guys back into this discussion. Some here repair Bosch CDI units and always tell us how great they are. Problem is the old CDI boxes really do fall short.

I ran a very solid stock ignition in my. 1973. MFI 911 for years.

The change to
C,D1 from Daytona-Sensors was a revelation...... Huge improvement!


Soft rev limiting is great.. Power, idle, starting all improved

In
My old Bosch is on the shelf.
If you drive your 911 get a modern CD I. .

I have to disagree. 40 year old components degrade. You can't argue with that. If they didn't then the boxes would never fail would they? One of the guys who works at Pelican has had his CDI box repaired four times!

CDI isn't used anymore for a number of reasons. Mostly because the strong spark catered for richly fuelled engines like the 911. We have better technology all round with leaner burns and yes, it isn't appropriate to modern engines. But it is totally appropriate to use it with an old fuel system like CIS, MFI and carbs. Yes the CDI spark is short compared to Kettering but we have addressed this by firing two sparks back to back.

Timing is important. Tired weights and springs may not be providing the curve that Porsche intended. Even if correct, the designed curve was for the fuel of the day and had a large safety margin built in. If you are sensible, running higher octane fuel allows you to reduce the safety margin and get better performance out of the engine. How do you think a Steve Wong chip works? Mostly different fuelling and timing. This is far from snake oil.

The problem with your 13mm wrench is that you will get better performance by advancing the distributor and adding a touch more fuel but your car will have a high idle. This is basic stuff guys.

The comment about detonation if the electronics fail depends on the design and applies to just about every ignition timing ECU ever made. Ours requires the microcontroller to be 'alive' for a spark to occur.

I'd really like the doubters to actually try one of our units. I am in discussions with a Socal specialist and they will shortly be receiving a couple of trial units. We have no affiliation with them. They will conduct independent testing.

VFR, our box has an output that can be configured to operate the fuel shut off at certain RPM (programmable).

The Turbos are an interesting case and we would certainly like to build in some control features for them.

Forgot to say, in response to 'cutting ignition not being appropriate for rev limiting'. It depends on how it is implemented.

We do this:

1). Soft limiter backs off advance, power fades off. You can feel this but can push through to the...
2). Hard limiter. This doesn't compltely cut the ignition. Sparks are fired on a cyclic basis, 1 in 5 being a good setting for a six cylinder engine. This prevents cylinder wash as the fuel is still burned periodically.

I run 6250 soft and 6500 hard on my SC with 964 cams. I have shift light blink on 6100.

See, these computer things are good for something! ;)

I'd say my Bosch CDI was 'tired'...the idle was often a bit lumpy was the key for me even tho everything is fresh/top end/fuel head/wur etc.
Changing to a new CDI stopped the lumpy idle immediately so I'd agree they do 'degrade' in increments.

I knew we would get the old school CDI guys back into this discussion. Some here repair Bosch CDI units and always tell us how great they are. Problem is the old CDI boxes really do fall short.

I ran a very solid stock ignition in my. 1973. MFI 911 for years.

The change to
C,D1 from Daytona-Sensors was a revelation...... Huge improvement!


Soft rev limiting is great.. Power, idle, starting all improved

In
My old Bosch is on the shelf.
If you drive your 911 get a modern CD I. .

This is what pisses me off.

If you would simply base your claims while kicked back in a lounge chair with a stiff tumbler of Scotch, with no real world testing, it would not muddy the waters.

Single Malt Scotch to be specific.

Been reading these debates for years. Some dyno testing would be interesting.

Below is from our old friend Grady

Chris is correct, the Petronics system is an improvement.
There are also improved CDI systems.
Our nice old 3-pin Bosch have very short rise-time (good for firing poor sparkplugs) but short duration (bad for lighting lean mixtures).
There is lots of discussion about the various systems.
The MSD seems to be on top of the short list.

Again, WELCOME.

Best,
Grady

1. Many/most D-Jetronic VW/Mercedes ECUs from the '60s (50 years+) are still
performing as initially designed. It all depends on the electronic design and what
components are avoided, e.g. electrolytic caps.
2. Bosch CDI units as with most electronics, fail for a number of reasons the least
of which is the result of aging.
3. The guy at Pelican is anecdotal evidence about rebuilt CDIs. Whether from any
of the rebuilders mentioned on Pelican, reports of vendor failures are basically
non-existent.

Having two consecutive sparks, or multiples, is still less effective than one longer
one as is generated from an inductive discharge ignition.

Since these "modern" CDIs are still using the timing information from a spinning
rotor shaft, i.e. points or a magnetic pickup, the crank position and RPM data come
only every 120 degrees of crank rotation which results in minimal improved
timing control. That's why all computer controlled ignition systems use a toothed
wheel to generate timing/RPM data, which without more RPM data, minimizes the
effectiveness of adding a micro 'C' to a CDI box.

Right, but the micro 'C' is still controlling the timing which is not the case for the
"passive" Bosch CDI. The micro 'C' system adds another timing failure mode.

So your "independent tester" will identify themselves and post directly to the Pelican
Parts forum the test results, right? Hopefully, analytical data such as the original
stock timing and the modified "modern CDI' timing will be provided.

Let's see...putting a Chevy LS-1 engine in my vintage 911 would get me better gas mileage, rock-solid cold start and it would smoke most early 911 with their poor stock engines. And I could pick up parts at the FLAPS on a Sunday afternoon....SWEEEEET

If I graft a quartz movement into my mechanic watch I would be able tell with much greater precision and no winding required.

Or I should just buy a Camaro and and a G-shock and get it over with.

hm - decisions, decisions, decisions

Mysocal911

Please list all the reasons Bosch cdi boxes fail.

Please delineate how the failure mechanism are not related to age (oxidation, corrosion, embrittlement, fatigue, seal degradation, high-cycle fatigue, thermal cycles)

A thought:

So cal folks really have no appreciation for how good they have it. Low humidity, warm.

Midwest, NE, Europe and elsewhere have to live with deep thermal cycles overlayed with rain, snow, salt and rapid humidity changes.

It's the -0C cold that really kills plastic and rubber, fiberglass. They get so stiff. They are much more likely to break and crack. Moisture is relentless, penetrating, corrosive.


Perhaps so cal experiences in longevity are not the norm, but the result of the ideal place for electronics to live.

The rest of us, well, deterioration, aging, is normal and expected.

The original CDI box failed on a low mileage (50K) 86 930 that I bought new. Never driven in rain, stored in a climate-controlled garage, never used as a daily driver, car was well-maintained, etc. It happens.

The new alternative looks like a good idea to me, regardless of what Mr. West thinks of it. I''ll probably also keep a spare on the shelf. I don't want to get to a point where I can't drive a car because I need something I can't get any more. Been there, done that, with other cars (now sold) so I may just stockpile a few critical items that I feel might be hard to find down the road.

JR

Based on data obtained from a CDI rebuilder:

1. Overcharging alternator - 40%
2. Reverse battery jumping - 25%
3. Owner shorted the coil wire - 10%
4. Bad engine ground connection - 10%
5. Capacitor failure (engine heat Turbos) - 10%
6. Intermittent solder connections - 5%

Geez. Such hostility! I want to know why anyone would be upset enough over a product that replaces an outdated component with improved performance, enhanced adjustability, and no requirement for altering the car to start demanding proof of testing, with or without single malt.
No need to mince words- you've all but called JH a liar and a cheat . I'm not hip to that.

I have a 1975 911 S. I intend to go with a complete EMS from bow to stern if I can afford it. Old-school technology is fine but I feel the benefits of modern technology are too strong to ignore, especially since they take into account the modern world's realities, like fuel quality.
If you've got a dog in this hunt then you should tell us which one it is. Otherwise, let the product or service speak for itself.

Rock on, Jonny.

Fully agree !
No one is imposing CDI+ on anyone... If you like it and you can afford it, you buy it !
I'm sure there will be a warranty to cover any failures during the first 1 or 2 years.

I have to laugh when people here start complaining about the increased possibility of failure whenever adding any modern electronics to our 911's. I would guess that 99% of the Pelicanites own another car and probably drive it daily... and if it was made in the last 20 years, it will have some kind of ECU... So what you do when it fails on the road ? You call the AAA or whatever.

If you really prize utmost reliability and "fixability", you probably should stick with Model T's...

Model T's were notoriously unreliable. Their saving grace was that you could fix them with baling wire and chewing gum and the occasional piece of rope.

You're right ! I was thinking more on the fixability side...

I blame that west guy. And his buddy socal9thing